The invention presented here concerns a process for the recovery and separation of gadolinium and gallium from scrap in the form of substances which contain both of these elements in the form of oxides or compounds which can be transformed to oxides, in particular gadolinium-gallium-garnet (GGG) which has the formula Gd.sub.3 Ga.sub.5 O.sub.12.
These substances are used mainly in the manufacture of components for bubble domain memory units. In the manufacturing stage about 80% of the starting material ends up as rejected material or scrap. This is waste material from a relatively expensive compound, and its recovery is of considerable economic interest. If the recovery and processing of the scrap leads to sufficiently pure products, then these can be recycled and used again as starting material. As a result, the economics of the production of GGG wafers can be improved considerably. Under the term "scrap" is to be understood particulate material (remainder of charges used to grow crystals, fragments of crystals from all stages of processing to wafer form) and also fines or powders which are formed during cutting, grinding, polishing etc. the garnet Gd.sub.3 Ga.sub.5 O.sub.12 or similar materials.
The digestion of such scrap is a problem which has existed for only a few years and one which has not been solved up to now. All previous attempts have failed because of the slow rate of dissolution of these complex oxides.